Function collect_elements_with_id 

fn collect_elements_with_id<E, Q, F>(
    root: E::ConcreteNode,
    id: &AtomIdent,
    results: &mut Q::Output,
    class_and_id_case_sensitivity: CaseSensitivity,
    filter: F,
)
where
    E: TElement,
    Q: SelectorQuery<E>,
    F: FnMut(E) -> bool,

Collects elements with a given id under root, that pass filter.